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Subject: Re: [REGRESSION] cdrom drive doesn't detect removal
From: Maxim Levitsky <maximlevitsky@gmail.com>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>, Tejun Heo <tj@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>
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Date: Tue, 21 Sep 2010 13:42:18 +0200
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On Thu, 2010-09-16 at 08:51 +0200, Kay Sievers wrote: 
> On Thu, Sep 16, 2010 at 00:20, Maxim Levitsky <maximlevitsky@gmail.com> wrote:
> > So it makes the sense.
> > It turns out that hal is still running on ubuntu systems, and yes, it
> > still polls the drives, and yes I disabled that feature....
> > So restoring that polling feature indeed fixes that problem for now.
> > Yet, why without that commit detection did work?
> 
> Really, I have no idea how this can happen. You could only find out
> with blocktrace, if something else is trying to open the device. The
> state change in the drive should not be able to get known to the host
> unless something is causing i/o with open().
> 
> Kay

Due to some unexplained laziness, I didn't put a printk to cdrom_open to
figure out if drive is polled or not without hal.
Today I finally found why kgdb didn't work (it was conflict with nmi
watchdog), and just for fun I have put a breakpoint to cdrom_open.
Well udisks *does* poll the drive, every few seconds, and therefore this
is a regression.
I will soon look at udisk source to see how it polls the drive.
(Maybe it uses exclusive open and hal doesn't or something like that.)

Best regards,
Maxim Levitsky